Method of processing a substrate and a device manufactured by the same

ABSTRACT

Provided is a substrate processing method capable of preventing over-etching of a part of a stair-case structure due to an etching solution, when a barrier layer is selectively formed on a VNAND device having the stair-case structure. The substrate processing method includes: alternately stacking a first insulating layer and a second insulating layer; forming a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface to the lower surface by etching the first insulating layer and the second insulating layer that are stacked; densifying the stepped structure; forming a barrier layer on the densified second insulating layer; and performing isotropic etching on at least a part of a sacrificial word line structure including the second insulating layer and the barrier layer. During etching the barrier layer at the isotropic etching step, the second insulating layer is not etched or etched a little to an ignorable degree.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2017-0153314, filed on Nov. 16, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND 1. Field

One or more embodiments relate to a substrate processing method using a thin film deposition technique and a device manufactured by the method, and more particularly, to a method of processing a substrate by depositing an insulating layer (e.g., a silicon nitride layer) on a substrate by a plasma-enhanced atomic layer deposition (PEALD) method and a device manufactured by the method (e.g., a semiconductor device).

2. Description of the Related Art

Recently, demand for three-dimensional (3D) vertical NAND (VNAND) flash devices has been rapidly increasing. In order to process more information, the number of times that a first insulating layer and a second insulating layer of a stack gate are stacked has increased to 32, 48, 64 pairs, and so on. A stack structure of insulating layers has a stair-case structure, and a metal wire may be connected to each step. For example, an upper surface of a second insulating layer is an upper surface of a stair-case structure, and the exposed second insulating layer is connected to a via contact hole.

However, when the via contact hole is formed, the via contact hole may be connected to another second insulating layer in the stair-case structure after penetrating through the second insulating layer due to excessive etching. This causes an electric short-circuit when driving a semiconductor device.

FIGS. 1A and 1B schematically show problems in the above processes. First insulating layers 2 a, 2 b, and 2 c (hereinafter, referred to as 2) and second insulating layers 3 a, 3 b, and 3 c (hereinafter, referred to as 3) are alternately stacked to form a stack structure 1. For example, the first insulating layers 2 may be SiO₂ layers, and the second insulating layers 3 may be SiN layers. The first insulating layers 2 insulate between gates (not shown). The second insulating layers 3 are connected to gate electrodes, and may be replaced with a metal layer such as tungsten, aluminum, etc. or other conductive layers in subsequent processes.

As shown in FIG. 1A, when a via contact hole 11 is formed, the via contact hole 11 may be connected to another second insulating layer 3 a after penetrating the second insulating layer 3 b due to excessive etching. As shown in FIG. 1B, when the second insulating layers 3 and a via contact hole 12 are filled with metal, an electric short-circuit may occur between the second insulating layers 3 a and 3 b, and accordingly, the device may not normally operate.

SUMMARY

One or more embodiments of the present disclosure are to form a protective layer selectively on regions of a structure having steps without performing a separate photolithography process.

One or more embodiments of the present disclosure are to prevent excessive etching in a part of the structure having steps, while forming a barrier layer.

One or more embodiments of the present disclosure are to improve resistance of upper and lower surfaces to wet-etching, in a stair-case structure of a three-dimensional (3D) semiconductor device.

One or more embodiments of the present disclosure are to prevent over-etching of the stair-case structure due to an etching solution, when a barrier layer is selectively formed on a vertical NAND (VNAND) device having a stair structure.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

According to one or more embodiments, a substrate processing method includes: alternately stacking a first insulating layer and a second insulating layer; forming a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface to the lower surface by etching the first insulating layer and the second insulating layer that are stacked; densifying the stepped structure; forming a barrier layer on the densified second insulating layer; and performing isotropic etching on at least a part of a sacrificial word line structure including the second insulating layer and the barrier layer.

The densifying of the stepped structure may include densifying an upper portion of the second insulating layer. The densifying of the upper portion of the second insulating layer may include selectively densifying a part of the second insulating layer, the part being at a boundary between the side surface and the lower surface of the stepped structure.

During the isotropic etching of at least a part of the sacrificial word line structure, a ratio between an etching rate of the part of the second insulating layer on the boundary between the side surface and the lower surface and an etching rate of the barrier layer may be equal to or less than a predetermined reference value.

During the isotropic etching of at least a part of the sacrificial word line structure, an etching rate of an exposed part in the second insulating layer on the upper surface and the lower surface of the stepped structure may be slower than an etching rate of an unexposed part of the second insulating layer.

During the isotropic etching of at least a part of the sacrificial word line structure, the part in the second insulating layer may be etched to a predetermined thickness or less, the part being on the boundary between the side surface and the lower surface.

The second insulating layer may include a first material, and the densifying of the stepped structure may include performing a plasma process by using a first gas as a reaction gas, the first gas including one of elements included in the first material.

An etching rate of the second insulating layer may be controlled by at least one of a kind and a flow rate of the first gas.

The first material may include a nitride material, and the first gas may include nitrogen.

The first gas may be a non hydrogen-containing gas. The densifying of the stepped structure may include performing a plasma process by using a second gas as a reaction gas, the second gas including at least one of the elements included in the first material, and the second gas may be a hydrogen-containing gas. An etching rate of the second insulating layer may be controlled by a supply ratio of the non hydrogen-containing gas and the hydrogen-containing gas, and may be adjusted to be slower than a predetermined reference etching rate, during the isotropic etching of at least a part of the sacrificial word line structure.

A hydrogen-containing gas may be used during the forming of the barrier layer on the second insulating layer, and a flow rate of the hydrogen-containing gas used during the forming of the barrier layer may be controlled such that a ratio between the etching rate of the part of the second insulating layer located on the boundary between the side surface and the lower surface and an etching rate of the barrier layer is equal to or less than a predetermined reference value.

The substrate processing method may further include: forming an interlayer insulating layer on the sacrificial word line structure; removing the sacrificial word line structure; and forming a conductive word line structure corresponding to a space from which the sacrificial word line structure is removed, wherein the conductive word line structure may include: a first conductive layer extending towards a channel; and a second conductive layer on the first conductive layer, wherein the densifying of the stepped structure may be performed by a plasma process, and in the first conductive layer, a part contacting the second conductive layer may have a thickness that is less than a thickness of a remaining part of the first conductive layer.

According to one or more embodiments, a substrate processing method includes: stacking a stack structure a plurality of times, the stack structure including an insulating layer and a first sacrificial layer; forming a stepped structure including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface to each other, by etching the stepped structure; forming a second sacrificial layer on the stepped structure; and performing isotropic etching on at least a part of the second sacrificial layer, wherein, before the forming of the second sacrificial layer, the first sacrificial layer is processed so that a density of an exposed part of the first sacrificial layer on the upper surface and the lower surface of the stepped structure is greater than a density of an unexposed part of the first sacrificial layer by a predetermined ratio or greater.

During the isotropic etching on at least a part of the second sacrificial layer, a ratio between an etching rate on the exposed part of the first sacrificial layer and an etching rate on the second sacrificial layer may be equal to or less than a predetermined reference value.

During the isotropic etching on at least a part of the second sacrificial layer, an exposed part of the first sacrificial layer on the upper surface and the lower surface may be etched to a predetermined thickness or less.

According to one or more embodiments, a substrate processing method includes: selectively densifying a stepped structure including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface to each other; forming at least one layer on the stepped structure; and performing isotropic etching on the at least one layer, wherein, before the isotropic etching, a ratio of hydrogen and nitrogen in the at least one layer is greater than a ratio of hydrogen and nitrogen in the stepped structure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:

FIGS. 1A and 1B schematically show problems in the existing processes;

FIGS. 2A to 2F are diagrams schematically showing processes of forming a protective layer on a stair-case structure of a three-dimensional (3D) semiconductor apparatus and selectively etching the protective layer;

FIGS. 3A and 3B are diagram schematically showing over-etching of a second insulating layer exposed on an upper surface of a stair;

FIG. 4 is a flowchart illustrating a substrate processing method according to an embodiment;

FIG. 5 is a schematic diagram illustrating a substrate processing method according to an embodiment;

FIG. 6 is a schematic diagram illustrating a substrate processing method according to an embodiment;

FIG. 7 is a schematic diagram illustrating a substrate processing method according to an embodiment;

FIGS. 8A to 8D are diagrams showing results of applying the substrate processing method of FIG. 5 on a pattern of stepped structure;

FIG. 9 is a schematic diagram illustrating a substrate processing method according to an embodiment;

FIG. 10 is a diagram showing a variation in a wet-etching rate of a second insulating layer according to a flow rate ratio of reaction gases used in the plasma pre-treatment of FIG. 9 (first and second steps);

FIG. 11 is a table showing conditions in each plasma pre-process of FIG. 10;

FIGS. 12 to 21 are schematic diagrams illustrating a substrate processing method according to an embodiment;

FIG. 22 is a diagram of a semiconductor device formed by the substrate processing method according to the embodiment;

FIGS. 23 and 24 are diagrams illustrating a substrate processing method according to embodiments and a semiconductor device manufactured by the substrate processing method; and

FIGS. 25 to 27 are diagrams illustrating the substrate processing method of FIG. 16 in more detail.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

Hereinafter, one or more embodiments of the present disclosure will be described in detail with reference to accompanying drawings.

Embodiments of the present disclosure are offered to illustrate more fully aspects of the present disclosure to one of ordinary skill in the art and the following embodiments may be modified in the form of a range of the aspect of the present disclosure, but is not limited to the following embodiments. Rather, these embodiments are provided to further enhance the present disclosure, and to illustrate completely the aspect of the present disclosure to those skilled in the art.

The terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the present disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, regions, and/or sections, these elements, regions, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, region, or section from another region, layer, or section. Thus, a first element, region, or section discussed below could be termed a second element, region, or section without departing from the teachings of exemplary embodiments.

In the present disclosure, “gas” may include vaporized solid and/or liquid, and may include single gas or a mixture of gases. In the present disclosure, a processing gas introduced into a reaction chamber through a shower head may include a precursor gas and an additive gas. The precursor gas and the additive gas may introduced into a reaction space typically as a mixture gas or separately. The precursor gas may be introduced with a carrier gas such as an inert gas. The additive gas may include a diluted gas such as a reactant gas and an inert gas. The reactant gas and the diluted gas may be introduced into the reaction space as a mixture or separately. The precursor may include two or more precursors, and the reactant gas may include two or reactant gases. The precursor is a gas that is chemisorped on a substrate and typically includes metalloid or metal elements configuring a main structure of a matrix in a dielectric layer, and the reactant gas for accumulation is a gas that reacts with the precursor that is chemisorped on the substrate when the gas is excited to fix an atomic layer or a monolayer on the substrate. “Chemisorption” denotes chemical saturated absorption. A gas other than the process gas, i.e., a gas introduced without passing through the shower head, may be used for sealing the reaction space, which includes a seal gas such as an inert gas. In some embodiments, “film” refers to a layer continuously extending in a direction perpendicular to a thickness direction substantially without pinholes to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, “layer” refers to a structure having a certain thickness formed on a surface or a synonym of film or a non-film structure. A film or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers.

In the present disclosure, the expression “containing Si—N bond” may refer to Si—N bonds or things specified by the Si—N bonds, and have Si—N bonds or a main skeleton substantially configured by Si—N bonds and/or Si—N bond or a substituent substantially configured by Si—N bonds. A silicon nitride layer may be a dielectric layer containing Si—N bonds, and may include a silicon nitride (SiN) layer and a silicon oxynitride (SiON) layer.

In the present disclosure, the expression “identical material” should be interpreted that main ingredients are identical. For example, when a first layer and a second layer are both silicon nitride layers formed of an identical material, the first layer may be selected from a group consisting of Si₂N, SiN, Si₃N₄, and Si₂N₃, and the second layer may be also selected from the above group, but detailed film quality of the second layer may be different from that of the first layer.

Additionally, in this disclosure, any two numbers of a variable may constitute a workable range of the variable as the workable range may be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments.

In the present disclosure where conditions and/or structures are not specified, one of ordinary skill in the art may readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. In all of the disclosed embodiments, any element used in an embodiment may be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present disclosure may equally be applied to apparatuses and methods.

Hereinafter, the embodiments of the present invention will be described with reference to the drawings which schematically illustrate the embodiments. In the drawings, for example, depending on a manufacturing technology and/or tolerance, modifications of illustrated shapes may be expected. Accordingly, it should be understood that the embodiments of the present disclosure are not limited to particular shapes in areas shown in the specification and may include, for example, changes in shape caused during a manufacturing process.

FIGS. 2A to 2F are diagrams schematically showing processes of forming a protective layer on a stair-case structure of a three-dimensional (3D) semiconductor device and selectively etching the protective layer;

In order to prevent a via contact hole from penetrating through a second insulating layer, as shown in FIGS. 2A and 2B, a barrier layer 6 is deposited on a stair-case structure 1. The barrier layer 6 may be deposited on a side surface S, an upper surface U, and a lower surface L of each step by a plasma-enhanced atomic layer deposition (PEALD) process. A plasma process is an in-situ plasma or a direct plasma process performed on a substrate. The plasma process is an asymmetric plasma process. According to a straight property of radicals and active species, the barrier layer deposited on the upper surface U and the lower surface L of the step is denser than the barrier layer deposited on the side surface S, due to the ion-bombardment effect.

Accordingly, as shown in FIG. 2C, the barrier layer on the side surface S is removed and the barrier layer on the upper surface U and the lower surface L of the stair-case structure remains after a wet-etching process (selective etching).

In addition, the barrier layer on a boundary between the upper surface U and the side surface S of the step and the barrier layer on a boundary between the lower surface L and the side surface S of the step have a film density in the middle of those of the barrier layer on the upper surface U and a barrier layer 8 on the side surface S, and thus, they remain as partially-left (or partially-removed) inclined overhangs 9.

After that, as shown in FIG. 2D, an insulating thick layer 10 is deposited on the stair-case structure 1, and via contact holes 11 are formed. Each of the via contact holes 11 is connected to the barrier layer 6 on a corresponding second insulating layer 3. Due to the barrier layer 6, penetration of the via contact hole 11 through the second insulating layer 3 may be prevented.

In post-processes, as shown in FIG. 2E, the via contact hole 11 is filled with metal to form a metal wiring 12. After that, as shown in FIG. 2F, the second insulating layer 3 and the barrier layer 6 are replaced with a conductive material, e.g., metal such as tungsten, aluminum, etc., polycrystalline silicon, or doped insulator to form a word line. As such, a gate electrode may be connected to the metal wiring 12 via a conductive layer 13.

However, during the selective etching, since only a part of the barrier layer 6 remains on the stair-case structure 1, for example, on the boundary between the lower surface L and the side surface S, the second insulating layer 3 under the barrier layer 6 may be partially exposed (see FIG. 2C). Therefore, the exposed part of the second insulating layer 3 may be etched and damaged due to an etching solution during the selective etching process, and becomes a cause for generating an electric short-circuit during driving of a device when the second insulating layer 3 is replaced with the conductive material.

FIG. 3 shows that the second insulating layer 3 exposed on the upper surface U and the lower surface L of a step is damaged due to over-etching.

In FIG. 3A, when the barrier layer 6 is selectively etched, the barrier layer 6 on the boundary between the side surface S and the lower surface L of the step is partially removed and a part 14 of the second insulating layer 3 is exposed to the etching solution. As shown in FIG. 3B, due to the exposed part 14 of the second insulating layer 3, the second insulating layer 3 may be damaged in various forms. For example, the second insulating layer 3 is partially removed (15), the etching solution infiltrating the second insulating layer 3 infiltrates along a boundary between the barrier layer 6 and the second insulating layer 3 to generate a void (16), or the second insulating layer 3 may be separated (17). In this case, when the second insulating layer 3 and the barrier layer 6 are replaced with the metal layer or the conductive layer in the post-process, the device may not normally operate and the second insulating layer 3 and the barrier layer 6 may not be used as the word line. Accordingly, the over-etching of a part of the second insulating layer during the etching process has to be addressed.

FIG. 4 is a flowchart illustrating a substrate processing method according to an embodiment.

Referring to FIG. 4, a stepped structure is formed (S1). For example, first insulating layers and second insulating layers are alternately stacked. Next, the stacked first insulating layers and the second insulating layers are etched to obtain the stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface.

After that, a plasma pre-treatment process is performed on the stepped structure (S2). The plasma pre-treatment process may be performed by using capacitive coupled plasma (CCP) that is excited by applying RF power to at least one of two electrodes. In an embodiment, the plasma pre-treatment may be performed in-situ in the same reactor for the process of forming the stepped structure, or may be performed ex-situ in different reactor from that for the process of forming the stepped structure.

In an embodiment, the plasma pre-treatment process may be performed by using an asymmetric plasma process, and a film quality of the upper surface of the stepped structure may be selectively densified by the asymmetric plasma process. The asymmetric plasma process includes a process of applying plasma to provide a directionality, and selective densification on a stepped structure may be achieved due to the plasma directionality.

For example, with respect to a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, the plasma may be applied in a direction parallel to the side surface. In this case, collision of plasma generally occurs on the upper surface and the lower surface of the structure due to the directionality, and the collision of plasma less occurs on the side surface of the structure.

In an embodiment, gas including argon (Ar) may be used during the asymmetric plasma process. During the asymmetric plasma process, the Ar gas is activated to generate active species. According to the directionality of the active species, the upper surface of the stepped structure, which is perpendicular to a direction of progress of the plasma active species, may be selectively densified, and accordingly, film quality of the upper portion of the stepped structure may have reinforced resistance against wet-etching. The densification may be generated by ion bombardment effect of the active species.

In another embodiment, during the asymmetric plasma process, a gas including a component of the stepped structure may be used. In detail, when the stepped structure includes a first material, a first gas may be used as a reaction gas to perform the plasma process, wherein the first gas contains one of elements included in the first material. For example, when the upper and lower surfaces of the stepped structure include silicon nitride layers, a gas (e.g., N₂, NH₃) including at least one (e.g., nitrogen) of the elements Si and N included in the upper surface of the stepped structure may be activated to generate the active species during the asymmetric plasma process. Due to the directionality of nitrogen plasma, the nitrogen plasma may be applied to the upper and lower surfaces of the stepped structure. Therefore, nitrogen component that is an element of the stepped structure increases, and thus, a nitrogen-rich silicon nitride layer may be obtained.

According to an embodiment, during the plasma pre-treatment process, the densification of the stepped structure may be achieved due to the ion bombardment effect of the Ar ions in the plasma and/or the reaction gas (for example, nitrogen ions). Here, a density and a wet etch rate (WER) characteristic of the stepped structure may be adjusted by varying plasma supplying conditions (plasma power, plasma frequency, Ar/N₂ flow rate, etc.).

Also, since hydrogen and nitrogen components are one of main elements affecting the resistance against the wet-etching (this will be described later with reference to FIGS. 9 to 11), the WER characteristic of the stepped structure may be adjusted by adjusting hydrogen and/or nitrogen amount in a reactant during the plasma pre-treatment process. For example, in order to reduce the WER of the silicon nitride layer, a gas that does not include hydrogen (or gas that does not include hydrogen component) may be used during the plasma process. Here, the gas itself may not include hydrogen gas, or components of the gas may not include hydrogen. For example, during the plasma pre-treatment on the silicon nitride layer, nitrogen gas not containing hydrogen (e.g., nitrogen (N₂) gas) may be used instead of ammonia (NH₃).

After that, a barrier layer is deposited on the stepped structure (S3). The barrier layer may be deposited by an atomic layer deposition (ALD) process, in particular, a PEALD process. The barrier layer may be an insulating layer. For example, the barrier layer may be a SiN layer. In one embodiment, the barrier layer may have a single layer. In another embodiment, the barrier layer may include a dual-layered structure or a composite layer formed with different processing conditions. Processes of forming the stepped structure and the barrier layer may be performed in-situ in the same reactor, or ex-situ in different reactors.

After that, a plasma post-treatment process may be performed (S4). The plasma post-treatment process may be performed by using capacitive coupled plasma (CCP) that is excited by applying RF power to at least one of two electrodes. In an embodiment, the plasma post-treatment may be performed in-situ in the same reactor with the processes of forming the stepped structure and the barrier layer, or may be performed ex-situ in different reactors.

The plasma post-treatment process may be performed by using the asymmetric plasma process, and the barrier layer may be selectively densified due to the asymmetric plasma process. The asymmetric plasma process includes a plasma application process to have directionality, and selective densification of a thin film deposited on a stepped structure may be achieved due to the plasma directionality.

For example, with respect to a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, the plasma may be applied in a direction parallel to the side surface. In this case, due to the directionality of the plasma active species, the barrier layer formed on the upper and lower surfaces of the stepped structure, wherein the barrier layer is perpendicular to the direction of process of the plasma active species, may be selectively densified. Accordingly, the resistance of the upper and lower surfaces of the stepped structure against the wet-etching may be increased greater than that of the side surface of the stepped structure.

Due to a difference between the film quality of the layer according to locations, wherein the layer is formed through the asymmetric plasma application, the barrier layer on the upper surface and the barrier layer on the lower surface may be separated during an isotropic etching process later (S5).

After the plasma post-treatment process, the wet-etching process may be performed (S5). In the present process, the barrier layer may be removed, and the removal of the barrier layer may be partially and selectively performed by using an etching solution (selective etching). That is, when the barrier layer is deposited on the stepped structure, the wet-etching process is performed, and thus, the barrier layer on the side surface is removed while the barrier layer on the upper and lower surfaces may remain.

As described above, the plasma post-treatment process is performed by using the asymmetric plasma process, the barrier layer may be selectively deposited on the upper and lower surfaces of the stepped structure only by the wet-etching process. Moreover, the barrier layer selectively formed may be sufficiently separated during the wet-etching process. Therefore, a photolithography process for forming the barrier layers selectively and to be spaced apart a predetermined distance from one another on the upper and lower surfaces of the stepped structure may be omitted.

When a part of the barrier layer is removed by the wet-etching, the stepped structure may be exposed to the etching solution at a location corresponding to the removed part. However, unlike in FIG. 3B, damage to the stepped structure (e.g., over-etching) due to the etching solution does not occur according to the present disclosure. This is because the plasma pre-treatment process is performed on the stepped structure in operation S2 before depositing the barrier layer to densify the stepped structure, and accordingly, the resistance against the wet-etching is improved.

According to an embodiment, the plasma pre-treatment may be performed by using the asymmetric plasma process. For example, with respect to a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, the plasma may be applied in a direction parallel to the side surface. In this case, when the barrier layer on the side surface is removed by the wet-etching, the side surface of the stepped structure exposed to the etching solution may be etched. However, unlike formation of the barrier layer with a predetermined interval by etching the barrier layer on the side surface, there is no need to etch the side surface of the stepped structure additionally, and thus, the plasma pre-treatment is not necessarily performed by using the asymmetric plasma process. This will be described in detail below with reference to FIGS. 25 and 26.

The wet-etching mentioned in the present specification is a method of etching a surface through a chemical reaction by immersing a structure of a semiconductor device into a liquid-type etching solution. The wet-etching is an isotropic etching method, and the isotropic etching itself may not largely affect the stepped structure and the selective etching of the barrier layer. Rather, according to the present disclosure, when the stepped structure and the barrier layer are formed, etch resistance of the stepped structure is improved through the plasma pre-treatment and the asymmetric plasma process is performed so that the upper and lower surfaces of the structure and the barrier layer thereon and the side surface of the structure and the barrier layer thereon may have different physical properties from each other, thereby achieving the selective etching in the post-etching process. In other words, processes performed before the etching process become elements of controlling the conditions of the wet-etching process.

The above elements controlling the processing conditions include a process of applying plasma. The selective etching of the stepped structure and the barrier layer may be achieved by applying at least one of the densification of the stepped structure and the barrier layer, directionality of the plasma, ion bombardment effect of active species, and/or application of gas plasma having a component included in the insulating layer as an element of controlling the post-etching process.

FIG. 5 is a schematic diagram illustrating a substrate processing method according to an embodiment.

Referring to FIG. 5, a method of improving resistance of the stepped structure against the wet-etching is provided. According to the present embodiment, a plasma pre-treatment is performed before depositing the barrier layer.

According to the present embodiment, the above method includes a first step, a second step, and a third step. The first step is the plasma pre-treatment process, the second step is a process of depositing the barrier layer, and the third step is a plasma post-treatment process.

In detail, in the first step, a substrate (stepped structure) is loaded in a reactor, and then, the plasma pre-treatment is performed on the substrate (stepped structure). The plasma pre-treatment activates a reaction gas as plasma by supplying the reaction gas without supplying a source gas. During one cycle of the first step, the reaction gas is supplied to the substrate (t0 to t2), and after that, the plasma may be applied to the substrate in a state where the reaction gas is supplied (t1 to t2). The ion bombardment effect of the activated reaction gas increases wet-etch resistance of a target layer. As shown in FIG. 5, a cycle including the supplying of the reaction gas (t0 to t2)/applying of plasma (t1 to t2)/purge (t2 to t3) is repeatedly performed a plurality of times (e.g., m times) to adjust the density of the stepped structure.

In an embodiment, a reaction gas may include at least one of the elements included in a film of an exposed lower substrate. For example, when a SiN insulating layer is exposed in the stepped structure, a gas including nitrogen may be used as the reaction gas. For example, the reaction gas may be N₂ or NH₃. When the gas including nitrogen (in particular, gas including nitrogen without hydrogen) is activated and applied to the stepped structure, the N component included in the stepped structure increases and a silicon nitride layer rich in nitrogen (N-rich) that is a component of the stepped structure may be obtained. In this case, density of the stepped structure may increase. Also, as described below, wet-etch resistance of the stepped structure may increase.

In an embodiment, the first step may include a reaction gas pre-flow process (t0 to t1). Through the pre-flow process of the reaction gas, the reaction gas may be evenly distributed in the reaction space before the plasma is supplied to the reaction space, and accordingly, the active species may be evenly distributed in the process of supplying plasma and the processes may be stably performed.

In another embodiment, the plasma pre-treatment process may be performed by using the asymmetric plasma process. For example, with respect to a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, the plasma may be applied in a direction parallel to the side surface. Here, since Ar ions or reaction gas ions have directionality (straight property), the ion bombardment effect shows greater on the upper and lower surfaces of the stepped structure (e.g., stair-case structure) than on the side surface of the stepped structure. Therefore, the upper and lower portions of the stair-case structure are more densified than a side wall and have relatively lower WER due to the plasma pre-treatment.

As described above, according to the embodiments of the present disclosure, the plasma pre-treatment is performed, and thus, the ion bombardment effect of the activated Ar ions and/or the densification effect of the thin film due to the nitrogen may be achieved, and accordingly, the resistance of the thin film against the post-etching process may be selectively adjusted.

The second step is a process of depositing the barrier layer on the substrate (that is, the stepped structure) on which the plasma pre-treatment is previously performed. The second step is a PEALD thin film deposition process. As shown in FIG. 5, a basic PEALD cycle including supplying of a source gas (t3 to t4)/purge (t4 to t5)/supplying of a reactant (t5 to t7)/RF plasma (t6 to t7)/purge (t7 to t8) is repeatedly performed a plurality of times (e.g., n times) to form the barrier layer with a desired thickness.

In the present embodiment, the source gas may be a precursor including Si, and in more detail, a precursor including an amino silane group. A gas including nitrogen may be used as a reactant. For example, the reaction gas may be N₂ or NH₃. However, the source gas and the reactant used in the present disclosure are not limited thereto. TSA, (SiH₃)3N; DSO, (SiH₃)2; DSMA, (SiH₃)2NMe; DSEA, (SiH₃)2NEt; DSIPA, (SiH₃)2N(iPr); DSTBA, (SiH₃)2N(tBu); DEAS, SiH₃NEt2; DIPAS, SiH₃N(iPr)2; DTBAS, SiH₃N(tBu)2; BDEAS, SiH₂(NEt2)2; BDMAS, SiH₂(NMe2)2; BTBAS, SiH₂(NHtBu)2; BITS, SiH₂(NHSiMe₃)2; TEOS, Si(OEt)4; SiCl₄; HCD, Si₂Cl₆; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H₂[N(Et)(Me)]2; AHEAD, Si_(t) (NHEt)6; TEAS, Si(NHEt)4; Si₃H₈, etc. may be used as the Si source, or combinations of the above materials may be used when supplying the Si source. In the present disclosure, the reactant may be a nitrogen gas including hydrogen, and NH4+ may be used in addition to the above-described NH₃. Ar is used as a purge gas.

After depositing the barrier layer with a desired thickness by repeatedly performing the second step a plurality of times, a plasma post-treatment using Ar gas may be performed in the third step. During one cycle of the third step, the Ar gas is supplied (t8 to 10), and after that, the plasma may be applied in a state where the Ar gas is supplied (t9 to t10). The above cycle may be performed a plurality of times (for example, x times). In the third step, the ion bombardment effect due to the Ar ions in the plasma may be achieved.

According to an embodiment, the plasma post-treatment may be performed by using the asymmetric plasma process. For example, with respect to a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, the plasma may be applied in a direction parallel to the side surface. Here, since Ar ions have directionality (straight property), the ion bombardment effect shows greater on the barrier layer on the upper and lower surfaces of the stepped structure (e.g., stair-case structure) than on the barrier layer on the side surface. Therefore, the barrier layer deposited on the side wall is not denser than the barrier layers deposited on the upper and lower portions of the stair-case structure and have relatively higher WER.

FIG. 6 is a schematic diagram illustrating a substrate processing method according to an embodiment. The substrate processing method according to the present embodiment may be a modified example of the substrate processing method according to the above-described embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 6, the barrier layer may be deposited on the stepped structure through plasma pre-treatment, PEALD barrier layer deposition, plasma post-treatment, and post wet-etching process. In the embodiment illustrated in FIG. 5, one reaction gas is used during the process of PEALD barrier layer deposition, but in the embodiment of FIG. 6, two reaction gases are used during the process of the PEALD barrier layer deposition.

A first step (plasma pre-treatment) may be performed by repeatedly performing supplying of reaction gas (t0 to t2)/plasma application (t1 to t2)/purge (t2 to t3) a plurality of times (for example, m times). After that, a second step (barrier layer deposition) may be performed by repeatedly performing the basic PEALD cycle including supplying of source (t3 to t4)/purge (t4 to t5)/supplying of reaction gas (t5 to t7)/RF plasma (t6 to t7)/purge (t7 to t8) a plurality of times (for example, n times).

As described above, the resistance of the stepped structure against the post wet-etching (or etching rate) may vary depending on kind and/or flow rate of the reactant used in the plasma pre-treatment, in particular, nitrogen and/or hydrogen amount included in the reactant. For example, a first reactant used in the plasma pre-treatment may be N₂ or NH₃. When N₂ is used as the first reactant, the WER of the stepped structure and a possibility of over-etching the stepped structure during the post wet-etching process would be less than those when NH₃ is used as the first reactant.

In the process of the PEALD barrier layer deposition, various materials or a combination thereof may be used as the reaction gas, and the resistance of the barrier layer against the post wet-etching may vary depending on the amount of nitrogen and/or hydrogen in the materials. For example, the first reactant may be N₂ and the second reactant may be NH₃, which may have higher resistance against the wet-etching than that the case where the first reactant is NH₄ and the second reactant is NH₃.

FIG. 7 is a schematic diagram illustrating a substrate processing method according to an embodiment. The substrate processing method according to the present embodiment may be a modified example of the substrate processing method according to the above-described embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 7, the barrier layer may be deposited on the stepped structure through plasma pre-treatment, PEALD barrier layer deposition, and post wet-etching process. In the embodiment of FIG. 6, the plasma post-treatment is performed after the PEALD barrier layer deposition. However, in the embodiment illustrated in FIG. 7, the post wet-etching process is performed without performing the plasma post-treatment.

As described above, the resistance of the stepped structure against the post wet-etching may vary depending on the kind and/or flow rate of the reactant used in the plasma pre-treatment.

Also, when the source material and the reaction gas used in the barrier layer deposition process (second step) are changed, the resistance of the deposited barrier layer against the post wet-etching may vary. Also, according to an embodiment, film quality of the barrier layer deposited on the stepped structure may be adjusted differently according to locations by adjusting the directionality of the RF plasma application (t6 to t7) performed in the barrier layer deposition process (second step).

FIGS. 8A to 8D are diagrams showing results of applying the substrate processing method of FIG. 5 on a stepped structure.

As shown in FIG. 8A, the stepped structure may be a stair-case structure 80 in which first insulating layers 81 a and 81 b (hereinafter, denoted by reference numeral 81) and second insulating layers 82 a and 82 b (hereinafter, denoted by reference numeral 82) are alternately stacked. The stair-case structure 80 may be obtained by alternately stacking the first insulating layers 81 and the second insulating layer 82 a plurality of times, and performing staircase etching on the stacked first and second insulating layers 81 and 82. The stair-case structure 80 has an upper surface U, a lower surface L, and a side surface S connecting the upper surface U and the lower surface L to each other.

According to an embodiment, the first insulating layer 81 may be a silicon oxide layer (SiO₂) and the second insulating layer 82 may be a silicon nitride layer (SiN).

The first insulating layer 81 a has a thickness h1, the second insulating layer 82 a has a thickness h2, the first insulating layer 81 b has a thickness h3, and the second insulating layer 82 b has a thickness h4. In an example, the thickness h1 of the first insulating layer 81 a and the thickness h3 of the first insulating layer 81 b may be equal to each other. In an example, the thickness h2 of the second insulating layer 82 a and the thickness h4 of the second insulating layer 82 b may be equal to each other. In an example, h1=h2=h3=h4 may be satisfied.

Referring to FIGS. 5 and 8B, a plasma pre-treatment process (first step) may be performed on the stepped structure (stair-case structure 80). Through the plasma pre-treatment (first step of FIG. 5), an exposed part of the second insulating layer 82 may be densified due to the ion bombardment effect of plasma. In detail, an upper portion of the stair-case structure 80, that is, the upper surface U, the lower surface L, and the side surface S, may be densified. As such, the wet-etch resistance of the upper portion of the stair-case structure 80 may be increased. In this case, during the post wet-etching process, the second insulating layer 82 may not be damaged or ignorable damage may occur, after that, an electric short-circuit may not occur when the second insulating layer 82 is replaced with a metal layer or a conductive layer.

Density of a part E in the second insulating layer 82 a, which is exposed to the plasma, may be greater than that of a part NE in the second insulating layer 82 a, which is not exposed to the plasma. In this case, an etching rate Ve of the part E of the second insulating layer 82 a exposed to the plasma may be less than an etching rate Vne of the part NE of the second insulating layer 82 a, which is not exposed to the plasma. Also, due to the ion bombardment effect, a thickness h2′ of the part E in the second insulating layer 82 a may be equal to or less than a thickness h2 of the part NE in the second insulating layer 82 a. That is, in the second insulating layer 82 a, the thickness h2 of the part contacting the first insulating layer 81 b may be equal to or thicker than the thickness h2′ of a part not contacting the first insulating layer 81 b. Accordingly, the thickness of the second insulating layer 82 a may change at a boundary between the lower surface L and the side surface S (85 of FIG. 8D), and the second insulating layer 82 a may have a stepped portion. Therefore, when a conductive word line structure is formed in the corresponding space where the second insulating layer 82 a and the barrier layer (83 of FIG. 8D) are removed, an upper portion of a first conductive layer (corresponding to the second insulating layer 82 a) of the conductive word line structure may have a stepped portion on an extending line perpendicular to an end of another first conductive layer (corresponding to the second insulating layer 82 b), and the stepped portion may be spaced apart from a second conductive layer (corresponding to a barrier layer 83). The conductive word line structure may have a first stepped portion (corresponding to 85 of FIG. 8D) on the first conductive layer.

Likewise, the second insulating layer 82 b of the upper surface U may be densified due to the ion bombardment after being exposed to the plasma, and may have increased resistance against the post wet-etching. Also, a thickness h4′ of the second insulating layer 82 b in the upper surface U exposed to the plasma may be equal to or less than the thickness h4 before being exposed to the plasma.

According to an embodiment, in order to improve the wet-etch resistance of the second insulating layer 82, a gas including one of the elements Si and N included in the second insulating layer 82 may be used as the reaction gas during the plasma pre-treatment, as described above. For example, the gas including nitrogen (N) may be used as the reaction gas. In this case, the nitrogen component that is included in the second insulating layer 82 increases due to the ion bombardment, and thus, a nitrogen-rich silicon nitride layer may be obtained. In this case, density of the second insulating layer 82, in particular, the second insulating layer 82 on the upper surface U and the lower surface L of the stair-case structure 80, may be increased.

As described above, the resistance of the stepped structure (in particular, the upper surface U, the lower surface L, and the side surface S) against the post wet-etching may vary depending on the kind and/or flow rate of the reaction gas used in the plasma pre-treatment (first step of FIG. 5). That is, an etching rate in a part of the second insulating layer 82 may be controlled by at least one of the kind and flow rate of the reaction gas. The etching rate on the exposed portion of the second insulating layer 82 may be controlled by adjusting at least one of the kind and the flow rate of the reaction gas, and thus, over-etching of a part in the second insulating layer 82 may be prevented during the post wet-etching process. That is, by adjusting at least one of the kind and the flow rate of the reaction gas, the second insulating layer 82 may be etched to a predetermined thickness or less during the post wet-etching process.

According to an embodiment, the plasma pre-treatment (first step of FIG. 5) may be performed by using the asymmetric plasma process. For example, the plasma may be applied to the stair-case structure 80 in a direction parallel to the side surface S. In this case, the plasma generally collides with the upper surface U and the lower surface L of the stair-case structure 80 due to the directionality, and may relatively less collide with the side surface S. Therefore, the density of the second insulating layer 82 on the upper surface U and the lower surface L may be greater than that of the second insulating layer 82 on the side surface S. In this case, when the barrier layer on the side surface S is removed by the post wet-etching process, the second insulating layer 82 on the side surface S of the stepped structure exposed to an etching solution may be etched. This will be described in detail below with reference to FIGS. 25 and 26.

According to another embodiment, the plasma pre-treatment (first step of FIG. 5) may include a process of selectively densifying at least a part of the second insulating layer on the upper surface U and the lower surface L. In particular, as described below with reference to FIG. 8D, since the second insulating layer 82 a is exposed to the etching solution at a boundary 85 between the lower surface L and the side surface S, the second insulating layer 82 on the boundary 85 may be selectively densified to prevent over-etching. For example, by adjusting the kind and/or the flow rate of the reaction gas used in the plasma pre-treatment (first step of FIG. 5), the second insulating layer 82 on the boundary 85 may be etched to a predetermined thickness or less during the post wet-etching process.

Referring to FIGS. 5 and 8C, the barrier layer deposition (second step of FIG. 5) is performed to deposit the barrier layer 83 on the stepped structure. The barrier layer 83 may be identical material to the second insulating layer 82. For example, when the second insulating layer 82 is a silicon nitride layer, the barrier layer 83 may also be a silicon nitride layer.

After that, the plasma post-process (third step of FIG. 5) is performed. In the present embodiment, the plasma may be applied to the stair-case structure 80 in a direction parallel to the side surface S. Here, due to the directionality (straight property) of the Ar ions, the barrier layer 83 on the upper surface U and the lower surface L and the barrier layer 83 on the side surface S may have different film quality from each other. That is, since the ion bombardment effect is concentrated on the upper surface U and the lower surface L and less concentrated on the barrier layer on the side surface S, the film quality varies depending on locations, and accordingly, the barrier layer 83 on the side surface S may be firstly etched during the post wet-etching process. As a result, the barrier layer 83 on the upper surface U and the lower surface L remains, and the selective wet-etching may be achieved.

In more detail, as shown in FIG. 8D, the barrier layer 83 on the side surface S may be primarily etched through the wet-etching, and accordingly, the first insulating layer 81 b and the second insulating layer 82 b on the side surface S may be exposed. In this case, the barrier layer on the upper surface U and the lower surface L may remain.

In addition, the barrier layer 83 on the boundary 85 between the upper surface U and the side surface S of the stair-case structure 80 has a film density in the middle of those of the barrier layer 83 on the lower surface L and a barrier layer 83 on the side surface S, and thus, the barrier layer 83 remains as inclined overhang 87, some of which remain (are removed). That is, the barrier layer 83 may be partially etched on the boundary between the lower surface L and the side surface S of the stair-case structure 80, and accordingly, the second insulating layer 82 a on the boundary 85 may be exposed.

However, even when the second insulating layer 82 a on the boundary 85 is exposed to the etching solution, damage to the second insulating layer 82 a (e.g., over-etching) does not occur. This is because the upper portion of the stepped structure is densified by performing the plasma pre-treatment on the exposed part of the second insulating layer 82 a in the first step before the barrier layer 83 deposition, and accordingly, the wet-etch resistance against the etching solution is increased.

According to an embodiment, the etching rate of the second insulating layer 82 a may be adjusted to be much slower than that of the barrier layer 83 by adjusting processing conditions of the plasma pre-treatment (first step of FIG. 5). In this case, the second insulating layer 82 would not be actually etched during the wet-etching process on the barrier layer 83.

In another embodiment, a ratio between the etching rate of the second insulating layer 82 and the etching rate of the barrier layer 83 may be adjusted to be equal to or less than a predetermined reference value by adjusting the processing conditions of the plasma pre-treatment (first step of FIG. 5). In particular, the ratio between the etching rate of the second insulating layer 82 a on the boundary 85 and the etching rate of the barrier layer 83 may be adjusted to be equal to or less than a predetermined reference value. In this case, the second insulating layer 82 would be etched to a predetermined thickness or less during the wet-etching process, and the over-etching may not occur on the second insulating layer 82.

FIG. 9 is a schematic diagram illustrating a substrate processing method according to an embodiment. The substrate processing method according to the present embodiment may be a modified example of the substrate processing method according to the above-described embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 9, the barrier layer may be deposited on the stepped structure through plasma pre-treatment, PEALD barrier layer deposition, and post wet-etching process. The embodiment illustrated in FIG. 7 includes one stage of the plasma pre-treatment, but the embodiment illustrated in FIG. 9 includes two stages of plasma pre-treatment.

A first step (first plasma pre-treatment) may be performed by repeatedly performing a cycle including supplying of a second reaction gas (t0 to t2)/plasma application (t1 to t2) a plurality of times (for example, m times). For example, a second reaction gas used in the first plasma pre-treatment may be N₂ or NH₃. After that, a second step (second plasma pre-treatment) may be performed by repeatedly performing a cycle including supplying of a first reaction gas (t2 to t4)/plasma application (t3 to t4) a plurality of times (for example, n times). For example, the first reaction gas used in the second plasma pre-treatment may be NH₃ or N₂. After that, a third step (barrier layer deposition) may be performed by repeatedly performing a basic PEALD cycle including supplying of source (t5 to t6)/purge (t6 to t7)/supplying of the first reaction gas and the second reaction gas (t7 to t9)/RF plasma (t8 to t9)/purge (t9 to t10) a plurality of times (for example, x times).

According to the present embodiment, two kinds of reaction gases are used in the plasma pre-treatment, and the plasma pre-treatment is divided as two stages, but the present disclosure is not limited thereto. For example, ‘a’ kinds of reaction gases may be used in the plasma pre-treatment and the plasma pre-treatment may be divided as ‘b’ stages (here, a is not necessarily equal to b).

According to an embodiment, the first reaction gas used in the second step may be different from the second reaction gas used in the first step. In more detail, a material having relatively low hydrogen amount may be used in the second step. According to an embodiment, a gas that does not contain hydrogen may be used as the first reaction gas and/or the second reaction gas, taking into account a factor that the hydrogen gas decreases the wet-etch resistance of the insulating layer. Also, nitrogen gas having low hydrogen content or not having hydrogen may be used as the first reaction gas and/or the second reaction gas. Moreover, the nitrogen content in the first reaction gas used in the second step may be greater than that of the second reaction gas used in the first step.

In one embodiment, when the second insulating layer includes a first material, a first gas including one of elements included in the first material may be used as a first gas to perform the plasma process shown in FIG. 9. In this case, the above element that is one of the components of the second insulating layer increases, and the density of the second insulating layer may increase. For example, when the first material is a nitride material, the first reaction gas may be a gas including nitrogen, and in this case, the second insulating layer may be formed as a nitrogen-rich insulating layer. The etching rate of the second insulating layer may be controlled by at least one of the kind and the flow rate of the first gas. For example, since the hydrogen component in the reaction gas restrains densification of a film and the nitrogen component in the reaction gas prompts densification of the film, a first gas including nitrogen may be used as the first gas or a first gas not containing hydrogen may be used as the reaction gas to increase the density of the second insulating layer. In an embodiment, a second gas including at least one of elements included in the first material may be used as the reaction gas to perform the plasma process of FIG. 9. As an example, the first gas may be a non hydrogen-containing gas and the second gas may be a hydrogen-containing gas. In this case, the etching rate of the second insulating layer may be controlled according to a flow rate ratio between the non hydrogen-containing gas and the hydrogen-containing gas. In particular, the flow rate ratio between the non hydrogen-containing gas and the hydrogen-containing gas may be adjusted so that the etching rate of the second insulating layer may be slower than a predetermined reference etching rate, while at least a part of a sacrificial word line structure including the second insulating layer (82 of FIG. 8C) and the barrier layer (83 of FIG. 7C) is isotropically etched.

As described below with reference to FIGS. 10 and 11, the density of the stepped structure (in particular, upper portion of the stepped structure) and resistance against the post wet-etching process (or etching rate) may change according to difference in processing parameters of the plasma pre-treatment processes (first and second step of FIG. 9). For example, when the first reaction gas is N₂ and the second reaction gas is NH₃, a WER is lower than that of a case in which the first reaction gas is NH₄ and the second reaction gas is NH₃.

FIG. 10 shows variation in the wet-etching rate of the second insulating layer exposed to the plasma, according to the kinds and/or flow rate ratio of the reaction gases used in plasma pre-treatment (first step of FIG. 7 and first and second steps of FIG. 9). FIG. 11 is a table showing conditions in each plasma pre-treatment of FIG. 10. In the present embodiment, the first insulating layer includes SiO2 and the second insulating layer includes SiN.

Conditions #1 to #3 are to only supply N₂ gas in the plasma pre-treatment (first step) according to the substrate processing method according to the embodiment illustrated in FIG. 7. Conditions #4 to #7 include supplying NH₃ as the second reaction gas in the first plasma pre-treatment and supplying N₂ as the first reaction gas in the second plasma pre-treatment, according to the substrate processing method of the embodiment illustrated in FIG. 9.

FIG. 10 shows WER of the second insulating layer under the plasma pre-treatment conditions #1 to #7. As shown in FIG. 10, a predetermined reference wet etch rate is 1.51 A/sec. When the second insulating layer has the WER greater than 1.51 A/sec, the second insulating layer that is exposed may be damaged (over-etched) during the wet-etching process on the barrier layer. Therefore, the etching rate of the second insulating layer has to be adjusted to be equal to or less than the predetermined reference speed (1.51 A/sec).

Referring to FIGS. 10 and 11, the WER of the second insulating layer according to conditions #4 to #7 is greater than that of the second insulating layer according to conditions #1 to #3. That is, the hydrogen gas weakens the wet-etch resistance of the insulating layer. When the gas including hydrogen is used, more Si—H bonds may be generated on the second insulating layer, and accordingly, the WER of the second insulating layer increases in the post wet-etching process.

In particular, when comparing condition #4 with condition #7, condition #4 and condition #7 are identical with each other except that a larger amount of NH₃ (3 L) is supplied in condition #7 than that of condition #4. Here, the WER of the second insulating layer in condition #7 is greater than that of condition #4 (1.38 vs. 1.36 A/sec). That is, as the hydrogen content in the reactant increases, the WER also increases.

When comparing condition #1 with condition #2, it is identified that the WER is decreased as the nitrogen content in the second insulating layer increases. Condition #2 is identical with condition #1, except that greater plasma power is applied than that of condition #1. In this case, due to the greater plasma power in condition #2, the second insulating layer (SiN) formed under condition #2 is denser than the second insulating layer (SiN) formed under condition #1 (for example, has more Si—N bonds), and accordingly, has smaller WER than that of condition #1.

That is, according to FIGS. 10 and 11, the hydrogen component in the reactant restrains the densification of the film and the nitrogen component of the reactant prompts the densification of the film.

Thus, the WER of a lower layer, that is, a part exposed to the plasma in the second insulating layer of the stair-case structure, may be controlled according to the kind and/or flow rate ratio of the reactants supplied in the plasma pre-treatment process. For example, a mixture gas of Ar and N₂ is supplied during the plasma pre-treatment without supplying hydrogen or a gas including hydrogen to reduce the WER of the second insulating layer, taking into account that the hydrogen gas degrades the wet-etch resistance of the insulating layer.

FIGS. 12 to 20 are schematic diagrams illustrating a substrate processing method according to embodiments. The substrate processing method according to the present embodiment may be a modified example of the substrate processing method according to the above-described embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 12, stack structures are stacked on a substrate 200 a plurality of times, wherein the stack structures respectively include insulating layers 210 a, 210 b, 210 c, and 210 d (hereinafter, denoted by reference numeral 210) and first sacrificial layers 220 a, 220 b, 220 c, and 220 d (hereinafter, denoted by reference numeral 220). For example, the insulating layer 210 may be a silicon oxide layer and the first sacrificial layer 220 may be a silicon nitride layer. However, the present disclosure is not limited thereto, and the insulating layer 210 and the first sacrificial layer 220 may include any materials having different etch selectivity from each other.

After that, the insulating layers 210 and the first sacrificial layers 220 are etched to form channel holes, and processes for forming at least a part of the components of a memory cell string (MCS of FIG. 22) in the channel holes are performed. The memory cell string may include such components as a channel, a gate conductive layer, and a gate insulating layer.

The process for forming the components of the memory cell string may be performed by directly forming at least a part of the channel, the gate conductive layer, and the gate insulating layer, by forming the sacrificial layer in the channel holes so that the channel, the gate conductive layer, and the gate insulating layer may be formed in post-processes, or by a combination thereof.

Next, the stack structure is etched to form a stair-case structure including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface to each other. For example, as shown in FIG. 13, an end portion of the stack structure including the insulating layer 210 and the first sacrificial layer 220 is etched to form a stepped structure having a stair shape. The stepped structure of the stair shape may be obtained by, for example, a reactive ion etching and resist slimming.

When the stepped structure of the stair shape is formed, the stepped structure includes an upper surface, a lower surface, and a side surface connecting the upper and lower surfaces. For example, the stepped structure may include at least one stair ST, and one stair ST includes an upper surface U on the first sacrificial layer 220 b, a lower surface L on the first sacrificial layer 220 a, and a side surface S connecting the upper surface U and the lower surface L to each other.

Referring to FIG. 14, a process of densifying the stepped structure of the stair shape, that is, plasma pre-treatment, is performed. The plasma pre-treatment may be performed by using an inert gas such as Ar and/or a gas including the component of the stepped structure (for example, nitrogen in a case where the first sacrificial layer 220 is a silicon nitride layer).

The plasma pre-treatment (that is, densifying process) may be performed by using the asymmetric plasma process. Due to the directionality of plasma ions in the asymmetric plasma process, only a part of the upper portion of the first sacrificial layer 220 (for example, a first silicon nitride layer), that is, the first sacrificial layer 220 (for example, a first silicon nitride layer) on the upper surface U and the lower surface L of the stair-case structure, may be densified. Therefore, selective etching of the sacrificial layer on the stepped structure may be achieved during the isotropic etching process.

According to an embodiment, at least a part of the first sacrificial layers 220 on the upper surface U and the lower surface L of the stepped structure may be selectively densified. For example, the first sacrificial layer 220 on a boundary between the side surface S and the lower surface L may be selectively densified. In another embodiment, conditions of the asymmetric plasma process are adjusted (for example, by adjusting the kind and/or flow rate of the reaction gas) so that a ratio between the etching rate of at least a part of the sacrificial layer 220 (for example, the first sacrificial layer 220 on the boundary between the side surface S and the lower surface L) and the etching rate of a second sacrificial layer (230 of FIG. 15) may be equal to or less than a predetermined reference value, and then, at least a part of the sacrificial layer 220 may be selectively densified. As such, during a post isotropic etching on the second sacrificial layer (230 of FIG. 15), at least a part of the first sacrificial layer 220 may be etched to a predetermined thickness or less.

In an alternative embodiment, before forming the second sacrificial layer (230 of FIG. 15), the first sacrificial layer 220 may be processed so that density of an exposed part on the upper surface U and the lower surface L may be greater than that of unexposed part of the first sacrificial layer 220. According to an embodiment, the first sacrificial layer 220 may be processed (for example, asymmetric plasma process) so that the density of an exposed part on the upper surface U and the lower surface L is greater than the density of the unexposed part of the first sacrificial layer 220 by a predetermined ratio or greater. A ratio between the etching rate of the exposed part of the first sacrificial layer 220 and the etching rate of the second sacrificial layer 230 may be equal to or less than a predetermined reference value by adjusting the density of the exposed part of the first sacrificial layer 220 in order to prevent over-etching of the first sacrificial layer 220 during the isotropic etching process. In this case, while the second sacrificial layer 230 is etched by the post isotropic etching process, the exposed part of the first sacrificial layer 220 on the upper surface U and the lower surface L may be etched to a predetermined thickness or less.

Referring to FIG. 15, at least one layer is deposited on the stepped structure of the stair shape. The at least one layer may be an insulating layer, and the insulating layer may be formed through the PEALD process according to the above-described embodiments. In this case, the second sacrificial layer 230 may be deposited on the stepped structure.

In one embodiment, the first sacrificial layer 220 and the second sacrificial layer 230 may have the same material. For example, when the first sacrificial layer 220 is a silicon nitride layer, the second sacrificial layer 230 may be a silicon nitride layer (that is, second silicon nitride layer).

In another embodiment, the second sacrificial layer 230 may have different physical property from that of the first sacrificial layer 220. For example, when the first sacrificial layer 220 and the second sacrificial layer 230 are respectively a first silicon nitride layer and a second silicon nitride layer, the non hydrogen-containing gas is used during the plasma pre-treatment and the hydrogen-containing gas may be used while forming the second sacrificial layer 230.

In an embodiment, flow rates of the non hydrogen-containing gas and the hydrogen-containing gas used during the forming of the second sacrificial layer 230 may be adjusted, so that the first sacrificial layer 220 may be etched to a predetermined thickness or less while the second sacrificial layer 230 is etched by the post isotropic etching, that is, so that the etching rate of the second sacrificial layer 230 may be faster than the etching rate of the first sacrificial layer 220 by a predetermined ratio or greater. For example, while the second sacrificial layer 230 is formed, ammonia may be supplied more than nitrogen. As such, a ratio of hydrogen and nitrogen in the second sacrificial layer 230 may be greater than a ratio of hydrogen and nitrogen in the first sacrificial layer 220. This is based on that the hydrogen component in the reactant restrains the densification of the film and the nitrogen component prompts the densification of the film (see FIG. 10). As such, the first sacrificial layer 220 may be etched to a predetermined thickness or less, during the isotropic etching on the second sacrificial layer 230.

After that, densification of the second sacrificial layer 230, that is, plasma post-treatment is performed. The plasma post-treatment process may be performed by using an inert gas such as Ar and/or a gas containing the component of the second sacrificial layer (for example, nitrogen when the second sacrificial layer 230 is a silicon nitride layer).

The plasma post-treatment may be performed by using the asymmetric plasma process. Due to the directionality of the plasma ions in the asymmetric plasma process, only the second sacrificial layer 230 on the upper surface U and the lower surface L may be densified. Therefore, selective etching of the second sacrificial layer on the stepped structure may be achieved during the isotropic etching process.

Referring to FIG. 16, a process of etching at least a part of the sacrificial word line structure including the first sacrificial layer 220 and the second sacrificial layer 230 (for example, the first silicon nitride layer and the second silicon nitride layer) is performed. The above etching may be an isotropic etching process. In more detail, the etching process may be performed by using the wet-etching process, for example, by using phosphoric acid or hydrofluoric acid.

Due to the asymmetric plasma post-treatment process, the etching rate of the second sacrificial layer (for example, the second silicon nitride layer) on a side surface S of a stair may be faster than the etching rate of the second sacrificial layer on the upper surface U and the lower surface L of the stair during the etching process. Therefore, the sacrificial layer on the side surface S is only removed, and the sacrificial layer on the upper and lower surfaces U and L may remain. As described above, a thin film (in this case, the second sacrificial layer) may be selectively deposited on the upper and lower portions of the stepped structure only by the asymmetric plasma post-treatment and the wet-etching process, without performing a photolithography process.

Also, during the etching process, the etching rate of the exposed part of the first sacrificial layer 220 may be slower than that of the second sacrificial layer 230. This may be because the first sacrificial layer 220 is densified during the plasma pre-treatment and the etch-resistance of the first sacrificial layer 220 is relatively improved, and/or because relative large amount of reactant containing hydrogen is supplied during the formation of the second sacrificial layer 230 and the second sacrificial layer 230 has a low density.

In one embodiment, the etching process may be performed according to one of following mechanisms.

-   -   First mechanism (a case where the upper surface U and the lower         surface L of one stair are only densified by the asymmetric         plasma pre-treatment, and the asymmetric plasma post-treatment         is performed): the second sacrificial layer 230 on the side         surface S of one stair is primarily removed. Accordingly, the         first sacrificial layer 220 and the insulating layer 210 on the         side surface S of the stair may be exposed to an etching         material (see FIG. 25). Here, the first sacrificial layer 220         and the insulating layer 210 on the side surface S exposed to         the etching material may be removed. This is because the first         sacrificial layer 220 and the insulating layer 210 on the side         surface S are not densified due to the asymmetric plasma         pre-treatment. Here, the second sacrificial layer 230 remaining         on the side surface S may be removed. Accordingly, the first         sacrificial layer 220 on the boundary between the side surface S         and the lower surface L of one stair may be exposed to the         etchant. However, the first sacrificial layer 220 exposed to the         etchant may not be removed or may be removed a little (for         example, to a predetermined degree). This is because the         asymmetric plasma pre-treatment is performed and the upper         portion of the first sacrificial layer 220 is densified (see         FIG. 26).

Therefore, when a conductive word line structure is formed in the corresponding space from which the sacrificial word line structure is removed, a first conductive layer (C1 of FIG. 20) of the conductive word line structure may not include a recess at the boundary between the side surface S and the lower surface L, but may have a relatively flat upper surface. However, since the side surface of the first sacrificial layer 220 is etched, a side surface of the first conductive layer (C1 of FIG. 20) would not be flat.

-   -   Second mechanism (a case where the upper surface U, the lower         surface L, and the side surface S of one stair are densified by         the plasma pre-treatment and the asymmetric plasma         post-treatment is performed): the second sacrificial layer 230         on the side surface S of one stair is primarily removed.         Accordingly, the first sacrificial layer 220 and the insulating         layer 210 on the side surface S of the stair may be exposed to         an etchant (see FIG. 27). Also, the first sacrificial layer 220         on the boundary between the side surface S and the lower surface         L of one stair may be exposed to the etchant. However, the first         sacrificial layer 220 and the insulating layer 210 exposed to         the etchant may not be removed or may be removed a little (for         example, to a predetermined degree). This is because the first         sacrificial layer 220 and the insulating layer 210 on the upper         surface U, the lower surface L, and the side surface S are         densified due to the plasma pre-treatment (see FIG. 26).

Therefore, when a conductive word line structure is formed in a corresponding space from which the sacrificial word line structure is removed, a first conductive layer (C1 of FIG. 20) of the conductive word line structure may not include a recess at the boundary between the side surface S and the lower surface L and in the side surface S, but may have a relatively flat upper and side surfaces.

In more detail, due to the asymmetric plasma post-treatment process, the second sacrificial layer 230 on the upper surface U and the lower surface L and the second sacrificial layer 230 on the side surface S have different physical properties from each other, and the second sacrificial layer 230 on the upper surface U and the lower surface L has greater wet-etch resistance than that of the second sacrificial layer 230 on the side surface S. Therefore, the second sacrificial layer 230 at the boundary between the upper surface U and the side surface S may protrude more than the side surface S, and the second sacrificial layer 230 at the boundary between the lower surface L and the side surface S may protrude towards the side surface S.

Also, when the first sacrificial layer 210 on the upper surface U and the lower surface L is not etched or is etched a little (for example, to a predetermined degree) because the plasma pre-treatment is performed, the first sacrificial layer 210 may not be damaged due to over-etching, and accordingly, the first sacrificial layer 210 may have a relatively flat upper surface.

The above first and second mechanisms are performed during a single etching process. That is, the substrate processing method according to the embodiments allows the thin film to be selectively deposited on the structure having steps without performing an additional photolithography process. Also, by adjusting the processing parameters in the plasma pre-treatment process, various types of damage such as over-etching may not occur on the stepped structure during selectively depositing a thin film.

Referring to FIG. 17, an interlayer insulating layer 250 is deposited on the sacrificial word line structure. The interlayer insulating layer 250 may include the same material as that of the insulating layer 210 between the first sacrificial layers 220 on the stepped structure. For example, the first sacrificial layer 220 of the stepped structure may be a silicon nitride layer and the insulating layer 210 of the stepped structure may be a silicon oxide layer, and then, the interlayer insulating layer 250 may be a silicon oxide layer.

Referring to FIG. 18, via contact holes 260 connected to at least a part of the second sacrificial layer 230 are formed in an upper surface of the interlayer insulating layer 250 through a patterning process. According to an embodiment, the via contact holes 260 may be formed after forming the conductive word line structure by etching the first and second sacrificial layers 220 and 230.

Referring to FIG. 19, the first sacrificial layer 220 and the second sacrificial layer 230 are etched, and then a channel (not shown), the insulating layer 210, the interlayer insulating layer 250, and the via contact holes 260 are exposed. Accordingly, the sacrificial word line structure including the first sacrificial layer (220 of FIG. 18) and the second sacrificial layer (230 of FIG. 18) may be removed. According to an embodiment, a second sacrificial layer (230′ of FIG. 18) on the substrate 200 may be also removed while etching the sacrificial layer, and accordingly, the upper surface of the substrate 200 may be partially exposed.

Referring to FIG. 20, a conductive word line structure WL is formed in the exposed space. The conductive word line structure WL may be formed in a corresponding space from which the sacrificial word line structure is removed. The conductive word line structure WL may include a material selected from various conductive materials such as tungsten, copper, polysilicon, etc., or a combination thereof.

The conductive word line structure WL may have following structure:

-   -   a first conductive layer C1 (corresponding to the first         sacrificial layer (220 of FIG. 18)) extending towards the         channel;     -   a second conductive layer C2 (corresponding to the second         sacrificial layer (230 of FIG. 18)) on an end portion of the         first conductive layer C1.

In other words, the first conductive layer C1 and the second conductive layer C2 included in the conductive word line structure WL are originated from layers formed through different processes (that is, sacrificial layers).

As described above with reference to FIG. 8B, according to the embodiments, the process of densifying the stepped structure, that is, the plasma pre-treatment, is performed before forming the second sacrificial layer. Therefore, the first sacrificial layer on the portion exposed to the plasma (that is, the upper surface U and the lower surface L of the stepped structure) has a height that is equal to or less than that of the first sacrificial layer on the portion that is not exposed to the plasma, due to the ion bombardment effect. Accordingly, as shown in FIG. 21, in the first conductive layer C1 of the conductive word line structure WL, a portion exposed to the plasma during the plasma pre-treatment may have a thickness that is equal to or less than that of a part that is not exposed to the plasma. As such, the first conductive layer C1 may have a first step S1. In detail, the first step S1 may be located on an extending line perpendicular to an end of another first conductive layer C1 that is located on the first conductive layer C1. Also, the conductive word line structure WL may have a second step S2 formed by the first conductive layer C1 and a second conductive layer C2 on the first conductive layer C1. The second step S2 may include an upper surface U1 of the second conductive layer C2, a side surface U2 of the second conductive layer C2, and an upper surface U3 of the first conductive layer C1. In one embodiment, the first step S1 and the second step S2 may be spaced apart from each other.

FIG. 22 is a circuit diagram of a semiconductor device according to an embodiment. The semiconductor device may be manufactured by the substrate processing method according to the above embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 22, a semiconductor memory device may include the substrate 200, a memory cell string MCS, a first word line WL1, and a second word line WL2.

The memory cell string MCS may extend as protruding from the substrate 200. The memory cell string MCS may include a plurality of memory cells. Although only four memory cells are shown in FIG. 22, more or less memory cells may be included in one memory cell string MCS.

The first word line WL1 may be connected to the first memory cell MC1. For example, the first word line WL1 may extend towards a channel of the first memory cell MC1. Likewise, the second word line WL2 may be connected to a second memory cell MC2, and the second word line WL2 may extend towards a channel of the second memory cell MC2.

At least one of the first word line WL1 and the second word line WL2 may include the word line structure formed through the processes illustrated in FIG. 20. Therefore, at least one of the first word line WL1 and the second word line WL2 may include the first conductive layer C1 extending towards the channel and the second conductive layer C2 on the first conductive layer C1, and in the first conductive layer C1, a part contacting the second conductive layer C2 has a thickness (h2′ of FIG. 8B) that is equal to or less than a thickness (h2 of FIG. 8B) of a part that does not contact the second conductive layer C2.

FIG. 23 is a diagram of a semiconductor apparatus formed by the substrate processing method according to the embodiment. The semiconductor device according to the embodiments may be modified examples of the semiconductor device according to the above-described embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 23, the semiconductor device is different from the semiconductor device of FIG. 20 in that a second sacrificial layer 230′ remains on the substrate 200. The second sacrificial layer 230′ on the substrate 200 may remain because the second sacrificial layer 230′ is not exposed to the etching solution during the etching process of the sacrificial layer shown in FIG. 19. In this case, the second sacrificial layer 230′ on the substrate 200 may be a structure remaining on a final product of the semiconductor device.

FIG. 24 is a diagram illustrating a substrate processing method according to an embodiment and a semiconductor device manufactured by the substrate processing method. The substrate processing method and the semiconductor device according to the present embodiment may be modified examples of the substrate processing method and the semiconductor device according to the above-described embodiments. Hereinafter, descriptions about the same elements of the embodiments will be omitted.

Referring to FIG. 24, the insulating layer 210 may be a silicon oxide layer and the sacrificial word line structure including the first sacrificial layer 220 and the second sacrificial layer 230 may include silicon nitride layers (that is, a first silicon nitride layer and a second silicon nitride layer). In order to separate the sacrificial word line structure on an upper portion of a stair-case structure ST and the sacrificial word line structure on a lower portion of a stair-case structure ST, a phosphoric acid etching process on a silicon nitride layer may be performed.

As shown in FIG. 24, during the phosphoric acid etching process, a second sacrificial layer may have a parallelogram-like overhang structure. This may be because, as described above, the etching rate of the second sacrificial layer on the upper surface U and the lower surface L of the stepped structure and the etching rate of the second sacrificial layer on the side surface S are different from each other due to the asymmetric plasma post-treatment.

Since the second sacrificial layer on a boundary 85 between the lower surface L and the side surface S is etched, the first sacrificial layer may be partially exposed. However, due to the plasma pre-treatment, the exposed part of the first sacrificial layer may not be etched or may only be etched to an ignorable degree during the phosphoric acid etching process. Accordingly, a cavity may not generate in the first sacrificial layer, and a possibility of separating and/or isolating the first sacrificial layer due to the etching may be reduced.

As described above, the substrate processing method according to the embodiments may prevent excessive etching of a stepped structure or generation of a cavity in the structure during processes of selectively forming a thin film on the stepped structure. As such, generation of electric short-circuit when the sacrificial layer of the stepped structure is replaced with a metal layer later may be prevented.

For convenience of comprehension, the shapes of each element in the accompanying drawings are exemplary. In addition, the above shapes may be variously modified. Throughout the specification, like reference numerals denote the same elements.

It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.

While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as defined by the following claims. 

What is claimed is:
 1. A substrate processing method comprising: alternately stacking a first insulating layer and a second insulating layer; forming a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface to the lower surface by etching the first insulating layer and the second insulating layer that are stacked; densifying the stepped structure; forming a barrier layer on the densified second insulating layer; and performing isotropic etching on at least a part of a sacrificial word line structure including the second insulating layer and the barrier layer.
 2. The substrate processing method of claim 1, wherein the densifying of the stepped structure comprises densifying an upper portion of the second insulating layer.
 3. The substrate processing method of claim 2, wherein the densifying of the upper portion of the second insulating layer comprises selectively densifying a part of the second insulating layer, the part being at a boundary between the side surface and the lower surface of the stepped structure.
 4. The substrate processing method of claim 3, wherein, during the isotropic etching of at least a part of the sacrificial word line structure, a ratio between an etching rate of the part of the second insulating layer on the boundary between the side surface and the lower surface and an etching rate of the barrier layer is equal to or less than a predetermined reference value.
 5. The substrate processing method of claim 1, wherein, during the isotropic etching of at least a part of the sacrificial word line structure, an etching rate of an exposed part in the second insulating layer on the upper surface and the lower surface of the stepped structure is slower than an etching rate of an unexposed part of the second insulating layer.
 6. The substrate processing method of claim 2, wherein, during the isotropic etching of at least a part of the sacrificial word line structure, the part in the second insulating layer is etched to a predetermined thickness or less, the part being on the boundary between the side surface and the lower surface.
 7. The substrate processing method of claim 1, wherein the second insulating layer comprises a first material, and the densifying of the stepped structure comprises performing a plasma process by using a first gas as a reaction gas, the first gas including one of elements included in the first material.
 8. The substrate processing method of claim 7, wherein an etching rate of the second insulating layer is controlled by at least one of a kind and a flow rate of the first gas.
 9. The substrate processing method of claim 7, wherein the first material includes a nitride material, and the first gas includes nitrogen.
 10. The substrate processing method of claim 7, wherein the first gas is a non hydrogen-containing gas.
 11. The substrate processing method of claim 10, wherein the densifying of the stepped structure comprises performing a plasma process by using a second gas as a reaction gas, the second gas including at least one of the elements included in the first material, and the second gas is a hydrogen-containing gas.
 12. The substrate processing method of claim 11, wherein an etching rate of the second insulating layer is controlled by a flow rate ratio of the non hydrogen-containing gas and the hydrogen-containing gas, and is adjusted to be slower than a predetermined reference etching rate, during the isotropic etching of at least a part of the sacrificial word line structure.
 13. The substrate processing method of claim 1, wherein a hydrogen-containing gas is used during the forming of the barrier layer on the second insulating layer, and a flow rate of the hydrogen-containing gas used during the forming of the barrier layer is controlled such that a ratio between the etching rate of the part of the second insulating layer located on the boundary between the side surface and the lower surface and an etching rate of the barrier layer is equal to or less than a predetermined reference value.
 14. The substrate processing method of claim 1, further comprising: forming an interlayer insulating layer on the sacrificial word line structure; removing the sacrificial word line structure; and forming a conductive word line structure in a corresponding space from which the sacrificial word line structure is removed, wherein the conductive word line structure comprises: a first conductive layer extending towards a channel; and a second conductive layer on the first conductive layer, wherein the densifying of the stepped structure is performed by a plasma process, and in the first conductive layer, a part contacting the second conductive layer has a thickness that is less than a thickness of a remaining part of the first conductive layer.
 15. A substrate processing method comprising: stacking a stack structure a plurality of times, the stack structure including an insulating layer and a first sacrificial layer; forming a stepped structure including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface to each other, by etching the stepped structure; forming a second sacrificial layer on the stepped structure; and performing isotropic etching on at least a part of the second sacrificial layer, wherein, before the forming of the second sacrificial layer, the first sacrificial layer is processed so that a density of an exposed part of the first sacrificial layer on the upper surface and the lower surface of the stepped structure is greater than a density of an unexposed part of the first sacrificial layer by a predetermined ratio or greater.
 16. The substrate processing method of claim 15, wherein, during the isotropic etching on at least a part of the second sacrificial layer, a ratio between an etching rate on the exposed part of the first sacrificial layer and an etching rate on the second sacrificial layer is equal to or less than a predetermined reference value.
 17. The substrate processing method of claim 16, wherein, during the isotropic etching on at least a part of the second sacrificial layer, an exposed part of the first sacrificial layer on the upper surface and the lower surface is etched to a predetermined thickness or less.
 18. A substrate processing method comprising: selectively densifying a stepped structure including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface to each other; forming at least one layer on the stepped structure; and performing isotropic etching on the at least one layer, wherein, before the isotropic etching, a ratio of hydrogen and nitrogen in the at least one layer is greater than a ratio of hydrogen and nitrogen in the stepped structure. 